EFFECT OF INTEGRATED USE OF RHIAZOBIUM INOCULATION, VERMICOMPOST AND PHOSPHORUS ON YIELD AND YIELD COMPONENTS OF COMMON BEAN (Phaseolus vulgaris L.) AT BAKO, WESTERN ETHIOPIA

Common bean (Phaseolus vulgaris L.) is an important food security crop in Ethiopia. However, the national average yield is very low owing to a number of abiotic and biotic stresses. Low soil fertility, coupled with limited fertilizer application practice by famers could be amongst the major one of the stresses that may caused for the low national mean yield of the crop in the country. Therefore, a field experiment was conducted at Bako to study the effect of integrated use of Rhizobium inoculated, vermicompost, and mineral phosphorus fertilizer on yield components and yield of common bean during the 2016 main cropping season. Factorial combination of three phosphorus rates (0, 46, 92 kg P2O5 ha-1), three vermicompost rates (0, 2.5, 5 ton ha-1) and Rhizobium inoculated (HP-429 strain) and without inoculated were laid out in randomized complete block design (RCBD) with three replications. Data on crop stand count, days to emergence, days to 50% flowering, days to 90% physiological maturity, plant height, number of primary branches, total number of nodules, nodule volume, effective number of nodules, nodule dry weight, aboveground dry biomass yield, number of pods per plant, number of seeds per pod, grain yield, 100 seed weight, and harvest index were collected and analyzed using Gen Stat statistical software. Thus, The main effect of phosphorus, vermicompost and Rhizobium inoculated HP-429 had significant influence on nodule dry weight of common bean. The two factor interaction effect of phosphorus and Rhizobium inoculated HP-429 significant variations in the effective number of nodules. On the other hand, three ways interaction of phosphorus, vermicompost and Rhizobium inoculated HP-429 rates significantly influences grain yield, pods per plant, seed per pod, physiological maturity, plant height, total number of nodules, nodule volume, of common bean were significantly affected by the three interaction effects of Rhizobium inoculated, Phosphorus and Vermicompost. Maximum common bean grain yield (3047 kg ha-1) was obtained from combination of Rhizobium strain of HP-429, 92 kg P2O5 ha-1 and 5 ton ha-1 vermicompost. Increasing patterns of yield parameters were observed in response to the increased rates of the phosphorus, vermicompost and with Rhizobium inoculated HP-429 strain. The maximum bean grain yields were obtained in response to the application of 92 kg P2O5 kg ha-1 + 5 t vermicompost ha-1 and Rhizobium inoculated with HP- 429 strain. Economically, the application of 46 kg P2O5 ha-1 + 2.5 t vermicompos t ha-1 and Rhizobium inoculated with HP-429 strain was found to be most profitable. Similarly, the adjusted grain yield of 2742.3 kg ha-1 was obtained in response to the application of 92 P2O5 kg ha-1 + 5 t vermicompost ha-1 and Rhizobium inoculated HP-429 strain. From this, it can be preliminary concluded that farmers in the study areas could sustainably enhance the yield of common bean by applying the recommended blanket phosphorus rate 46 kg P2O5 ha-1, 2.5 t vermicompost ha-1 in combination with Rhizobium inoculated HP-429 strain. This combined application rates organic, inorganic and bio-fertilizer save farmers the cost of the expensive inorganic phosphorus and nitrogen fertilizers as well as use for subsequent crops. However, it is suggested that the experiment has to be repeated over seasons and locations using this and other improved common bean varieties to make a conclusive recommendation